Dental tool chuck

ABSTRACT

A dental handpiece for rotatably driving a dental tool includes a sheath housing a chuck which releasably holds the dental tool to the handpiece and a push button in operative contact with the chuck to operate the chuck to move the chuck between a looked and unlocked position. The push button is in the form of a ring which slides in a plane perpendicular to the axis of the sheath. The chuck includes a bur tube rotatably received in the sheath, a tilt plate which extends through side openings in the bur tube, and a tilt plate pusher which is received in the sheath and through which the bur tube extends. The tilt plate pusher has a side hole through which an arm of the tilt plate extends, such that movement of the tilt plate pusher will pivot the tilt plate. A head of the tilt plate pusher is in operative contact with the push button, such that when the push button is pressed, the tilt plate pusher will be moved forwardly to move the tilt plate from a locked to an unlocked position.

TECHNICAL FIELD

This invention relates to medical/dental handpieces, and in particularto a chuck for the handpiece which releasably holds and drives a curing,polishing, or grinding tool. In its broader aspects the invention mayalso find application in other chucking systems which hold and rotateshafts.

BACKGROUND OF THE INVENTION

Dental handpieces include both high speed turbine types (typically200,000 to 400,000 rpm) having an air motor and gear-driven lower speedtypes (typically, 1,000 to 15,000 rpm) having an air motor or anelectrical motor. Both have long employed collet chucks for releasablyholding dental burs which cut, grind and polish teeth. Similar burs areused in surgery for performing these functions on bone. Because theshafts of dental tools are quite small and quite closely toleranced(shaft diameters between 0.0626" and 0.0630"), and because the demandsof dental and surgical procedures require the utmost performance, colletchucks are high precision devices requiring a great deal of care andexpense for their manufacture. The collet chucks include a tube whichaligns the bur and radially movable fingers which hold the shaft of thebur both axially and rotationally. The tube, fingers, and the operatingmechanism for the fingers must be formed precisely.

The chucks commonly used in dental (or surgical) handpieces generallyfall into two groups: those including a positive screw thread adjustmentfor tightening and loosening the fingers of the chuck, and those whichuse a spring for tightening the chuck and some mechanism for looseningthe spring. Both types of chucks have drawbacks. The threaded typerequires a separate wrench which is difficult to handle, must beseparately sterilized, and must be accounted for. When used with aturbine handpiece, a mechanism must be provided in the wrench orotherwise for holding the driven rotor of the turbine from rotationwhile turning the threaded member. The spring-biased type requires ameans for opening the fingers against the spring force; a spring forcegreat enough to hold the bur shaft reliably requires exerting a greatdeal of effort to open the fingers. U.S. Pat. Nos. 3,637,050 toHoffmeister, 4,874,314 to Fleer et at., 5,040,980 to Heil, and 5,090,906to Pernot. The first two patents utilize a push button to open thechuck, and the latter two patents utilize lever arms to reduce theeffort required to open the chuck. The problems with spring-biasedcollet chucks are described some detail in Heil, U.S. Pat. No.5,040,980. As further described in that patent, the force required topull the bur shaft from the chuck when the bur is not mining is notnecessarily a good predictor of how well the chuck will hold in actualuse of the bur on tooth or bone. The problems are further compoundedwhen the bur is used on disparate materials such as amalgam or the thinmetal shell making up dental crowns, which can grab the bur.

Alternatives to the collet chuck have been proposed for dental angles.Examples are the expansible polyethylene sleeve shown in U.S. Pat. No.3,324,553 to Borden, and the coil spring shown in U.S. Pat. No.4,021,918 to Bailey. None of the alternatives, however, has provided therequired precision and resistance to slippage and pull-out.

SUMMARY OF THE INVENTION

One object of the present invention is to provide a simple, effectivechuck for releasably holding a dental tool in a handpiece.

Another object is to provide such a chuck which is easy to operate.

Another object is to provide such a chuck which will substantiallyprevent rotational and axial slippage of the tool in the chuck.

Another object is to provide such a chuck which is easy to construct andeconomical to produce.

Other objects will become apparent to those skilled in the art in lightof the following disclosure and accompanying drawings.

In accordance with one aspect of the invention, generally stated, achuck is provided for a dental handpiece to releasably secure a dentaltool in the dental handpiece. The chuck includes a hollow bur tube whichreceives the dental tool. The bur tube is rotatably fixed to a drivenmember and has first and second aligned radial openings formed in a wallof the bur tube. The second opening is larger than the first. A firplate is received in the bur tube. The tilt plate has a tilt plate body,a first finger received in the first radial opening and a second fingerextending through the second radial opening. A tool opening, throughwhich the tool extends, extends generally axially through the tilt platebody. The tool opening is defined by a surface having at least one edge.The tilt plate is moveable between a first, unlocked, position in whichthe edge is spaced slightly from the dental tool so that the tool may befreely moved axially relative to the tilt plate, and a second, locked,position in which the edge contacts the tool to prevent axial androtational movement of the tool relative to the tilt plate.

Preferably, a generally cylindrical tilt plate pusher is received aboutthe bur tube. The tilt plate pusher is in operative contact with thetilt plate and is movable axially relative to the bur tube to move tiltplate between its locked and unlocked positions. In some embodiments, aspring biases the tilt plate to its locked position, and a push buttonis provided which is used to operate the tilt plate pusher to move thetilt plate to its unlocked position. In another embodiment, a screwthread mechanism locks the tilt plate.

Preferably, the dental handpiece has an arm housing a drive and a headhousing a driven member (generally either a gear or a turbine) inoperative contact with the drive. The chuck is rotatably received in thedental tool head to be operatively connected to the driven member to berotated by the driven member. The chuck may also be utilized in otherportions of a gear-driven handpiece.

In one embodiment, the driven member has a hollow head. The bur tube isfixed to the driven member so that the driven member head and the burtube define an annular channel. The bur tube radial openings may bepositioned above the driven member or in the channel. In the formercase, a spring is received in the channel, beneath the tilt plate, tooperatively engage the tilt plate second finger to bias the tilt plateto its locked position. In the latter case, the tilt plate fingerextends into the channel and the tilt plate and bur tube define a secondchannel. In this case, the spring is located above the second finger tobias the tilt plate to its locked position. In either case, a springspacer is preferably positioned between the spring and the tilt platesecond finger. The spacer may have a slot formed therein which isaligned with the first bur tube radial opening so that the spacer doesnot contact said tilt plate first finger.

In a third embodiment, the tilt plate pusher is received within the burtube.

In another embodiment, the bur tube and tilt plate pusher have engagingthreads. Thus, when the tilt plate pusher is rotated in a firstdirection, the tilt plate pusher moves toward the .lilt plate to movethe tilt plate to its locked position and hold the tilt plate there.When it is rotated in the opposite direction, the tilt plate pusher ismoved away from the tilt plate and the tilt plate falls to its unlockedposition. The tilt plate pusher includes a top having a groove formedtherein. The push button is rotatable and includes a rib which engagesthe tilt plate pusher groove when the push button is pushed downwardly.The push button is spring biased to be out of engagement with the tiltplate pusher. This embodiment has the benefit that it positively retainsthe tilt plate in its locked position.

In another aspect of the invention, the tilt plate is incorporated in adental handpiece for rotatably driving a dental tool or a dentalattachment. The handpiece includes a sheath housing a chuck whichreleasably holds the dental tool or dental attachment to the handpieceand a push button in operative contact with the chuck to operate thechuck. The sheath has an annular slot in an outer surface in which thepush button slides, and the slot has a pair of opposing flat surfaceswhich are offset from a center of the sheath. The push button is in theform of a ring having a pair of inner flat surfaces which are longerthan the sheath tilt surfaces, so that the push button may be movedrelative to the sheath between a first position in which the chuck is ina locking mode, and a second position in which the chuck is in a releasemode. The push button is normally biased to the first position.

A bur tube is rotatably received in the sheath. The bur tube has aforward opening sized to receive a shaft of the dental attachment ordental tool. The bur tube also has a pair of oppositely disposed sideopenings, one of which is larger than the other. A tilt plate ispivotably rcceived in the bur tube. The tilt plate has a first armreceived in one of the bur tube openings and a second arm received inthe other of the bur tube openings. The tilt plate has a central openingdefined by at least one edge through which the shaft of the dental toolor attachment extends. The tilt plate is movable between a lockedposition in which the edge contacts the shaft to secure the dental toolor attachment to the handpiece, and an unlocked position in which theedge is generally coaxial with the shaft, to allow movement of the shaftrelative to the handpiece. A tilt plate pusher is slidable axiallyrelative to the bur tube and is in operative contact with the pushbutton and the tilt plate. The tilt plate pusher is moved by the pushbutton to move the tilt plate between its locked and unlocked positions.The sheath includes a least one slot through which a head of the tiltplate pusher having a head extends to place the tilt plate pusher inoperative contact with the push button. Thus, when the push button ispressed, the push button will press against the tilt plate head and movethe tilt plate axially in the sheath,

The tilt plate pusher has an opening in a side thereof through which anarm of the tilt plate extends. The tilt plate pusher slot is positionedsuch that when the tilt pat pusher is moved axially forwardly, a rearedge of the slot contacts the tilt plate arm to move the tilt plate fromits locked to its unlocked position. The tilt plate pusher is biasedrearwardly, and the tilt plate pusher slot is sized such that when thetilt plate pusher is moved rearwardly, a front edge of the flit platepusher slot will contact the tilt plate arm to move the tilt plate fromits unlocked to its locked position.

Preferably, the flit plate pusher is formed as a hollow tube throughwhich the bur robe extends to be operatively connected to a motor unit.A drive connector is provided which connects the bur tube shaft to themotor; the drive connector having a rearwardly extending shaft which isreceived by the motor.

It has been found that the chuck of the present invention provides asurprisingly firm grip on the shaft of a dental tool under operatingconditions, while being easier to operate than conventional colletchucks, and that it provides the accurate and secure alignment of thebur required for dental and medical operations on calciferous structuressuch as tooth and bone, and for dental laboratory work.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a dental handpiece angle attachmentwith one illustrative embodiment of a chuck of the present invention;

FIG. 2 is an exploded view of the attachment;

FIGS. 3-5 are front, side, and back elevational views of a bur tube ofthe attachment;

FIG. 6 is a top plan view of the bur tube;

FIG. 7 is a perspective view of a tilt plate pusher of the attachment;

FIGS. 8 and 9 are perspective and side elevational views of a springspacer of the attachment;

FIG. 10 is an enlarged, exaggerated schematic drawing showing theengagement of a tilt plate with a tool to hold the tool in theattachment;

FIG. 11 is a cross-sectional view of a handpiece with a secondembodiment of the chuck;

FIG. 12 is a cross-sectional view of a the attachment with a thirdembodiment of the chuck;

FIGS. 12A-C are cross-sectional views of the third embodiment of thechuck, demonstrating operation of the chuck;

FIG. 13 is an exploded view of the chuck assembly of the thirdembodiment;

FIGS. 14 and 15 are side and from elevational views of a tilt platepusher used with the third embodiment;

FIG. 16 is a side elevational view of an outer stationary bar tube ofthe third embodiment;

FIGS. 17-18 are top plan and side elevational views of a tilt plate ofthe attachment;

FIGS. 19-20 are top plan views showing alternate designs for the tiltplate;

FIG. 21 is an enlarged cross-sectional view of the attachment with afourth embodiment of the chuck;

FIGS. 22-25 are schematic drawings showing the use of two or more tiltplates in the chuck;

FIG. 26 is a cross-sectional view of a dental handpiece, which accepts adental attachment, incorporating a push button release mechanism;

FIG. 27 is an exploded view of the handpiece of FIG. 26; and

FIG. 28 is a top plan view of a center sheath of the handpiece.

BEST MODE FOR CARRYING OUT THE INVENTION

A dental handpiece head assembly 1 of the present invention is shown inFIGS. 1 and 2. Assembly 1 is shown to be a dental angle and includes aone piece body 3 having a sleeve 5 and a head 7. Sleeve 5 is hollow andreceives a face gear 9 which, in operation, is operatively connected toa drive system by its shaft 11. A spline knee 13 and adjusting nut 15are secured to the back of the sleeve 5 to secure the assembly to adental handpiece 2. Although the invention is shown incorporated into adental angle, it will be appreciated by those skilled in the art that itcould be used with other dental instruments which rotatably receive adental tool.

Head 7 is hollow and has upper and lower openings 16 and 18,respectively. Head 7 holds a chuck assembly 21 which removably secures adental tool 23 having a shaft 24, such as a bur, prophy cup, prophyangle, file, reamer, etc., in the head. Chuck assembly 21 is rotatablymounted in the head to drive the tool. Preferably, the chuck extendsthrough two ball bearings 25 and 95. Ball bearing 25 sits on a shoulder27 defined at the bottom of head 5 and which surrounds lower opening 18.Ball bearing 95 is positioned at the top of the head.

Chuck assembly 21 includes a driven gear 29 which is rotatably journaledin the bearing 25. Gear 29 has a hollow stem 31, which extends throughbearing 25 and opening 18, and a head 33 having teeth 35 which mesh withdrive gear 9. Head 33 is larger in diameter than stem 31 and extendsradially outwardly of stem 31 and over ball bearing 25. Gear head 33 ishollow, having an annular wall 36 on which teeth 35 are formed and afloor 38 defined by the top surface of stem 31.

A hollow bur tube 37 is fixedly received in, and extends through, gearstem 31. Preferably, bur tube 37 is force fitted into stem 31 to berotatably fixed to gear 29. Other means to rotatably fix bur tube 37 tostem 31 (such as soldering, gluing or pinning) could of course be used.Bur tube 37 removably receives tool 23. Tube 37 and gear annular wall 36cooperate to define an annular channel 40. Bur tube 37, which is moredearly shown in FIGS. 3-6, includes a body portion 39 and a head portion41.

A bore 42, into which tool 23 is inserted, extends through tube 37. Bore42 has a counter-bore 42a at the top of tube 37. Body portion 39 isstepped midway up the body, as at 43, to define a shoulder 44 which sitson gear head floor 38. An opening 45 is formed in bur tube body 39slightly below head 41. As shown, opening 45 is generally rectangular. Asecond, smaller, generally circular opening 47 is formed in body 39spaced from opening 45. Opening 45, as best seen in FIG. 3, has a heightgreater than the height of opening 47. Counter-bore 42a extendsdownwardly to a point slightly below the bottom of openings 45 and 47.Head portion 41 is larger in diameter than body portion 39 and includesa pair of oppositely disposed axially extending grooves 51. Preferably,grooves 51 have a depth so that their floors are coplanar in flush withthe outer wall of body 39.

A hollow plug 53 is received in bur robe bore 42a in the bur robe head41. Plug 53 extends from the top of the bur robe to approximately thetop of the bur tube opening 45. Plug 53 has a bore 52 which iscounter-bored to form a shoulder 54 (FIG. 1), forming a stop whichprevents tool 23 from being pushed too far into tube 37. The diameter ofthe plug bore is substantially the same as the diameter of tube bore 42,both of which have a diameter slightly larger than the shaft of thedental tool to concentrically hold the dental tool in chuck 21.

Although plug 53 is preferably formed separately from bur tube 37, theplug and bur tube can be formed as a single piece. In this case, the burrobe bore 42 would be counter bored in head 41 to define shoulder 54.

A tilt plate 55 (shown more clearly in FIGS. 18 and 19) is received inbur tube 37 generally transverse to the axis of tube 37. Tilt plate 55includes a generally annular body 57 which is sized to pass through burrobe opening 45 and be received within bore 42a. Body 57 is slightlylarger in diameter than tube bore 42, thus bore 42a defines a pocket inthe tube which receives the tilt plate body 57. The tilt plate body 57has an inner wall 59 defining a hole 61 through which tool 23 isslidably journaled. A first finger 63 extends radially from body 57 andprotrudes through bur tube opening 45. A second smaller finger 65extends radially from body 57 into bur tube opening 47. Due to the sizedifferences in bur tube openings 45 and 47, finger 65 defines a pivotpoint for plate 55 about which tilt plate 55 can pivot vertically.

As seen in FIG. 10, the tilt plate is movable between two positions. Inone position, tilt plate inner wall 59 is angled with respect to theaxis of tool 23 so that the edges 67 of the tilt plate wall 59 contactstool 23. This contact, as will be explained below, is strengthened orenforced so that the tool 23 is frictionally held in chuck 21 to berotatably driven as the chuck is turned by the drive mechanism. The tiltplate's grip of the dental tool is sufficiently strong so that the toolwill not move rotationally or axially relative to the tilt plate whilethe tool is in use. In the second position (shown in phantom) the tiltplate wall 59 is parallel to or coaxial about the tool 23 so as to bespaced therefrom. In this position, the tool can be moved relative tothe tilt plate 55 so that a tool can be inserted or removed from thechuck assembly 21. Although the tilt plate wall is shown to be parallelto tool shaft 24 in the unlocked position, all that is necessary is thatthe edges be spaced from shaft 24 a distance sufficient to allow thetool to be moved axially.

Tilt plate wall 59 is preferably formed so that it is perpendicular tothe top and bottom surfaces of the tilt plate 55. Thus, the tilt plateis in its locking position when it is tilted relative to the tool. It isin its unlocked position when plate 55 is generally perpendicular to thetool, as shown in FIG. 10. The tilt plate could alternatively be formedso that the wall 59 is not perpendicular to the tilt plate's top andbottom surfaces. In this case, the tilt plate would be in its lockedposition when generally perpendicular to the tool, and in its unlockedposition when tilted relative to the tool. The tilt plate wall couldalso be formed so that the tilt plate is tilted relative to the dentaltool in both its locked and unlocked positions. This difference betweenthe preferred tilt plate and the two latter tilt plates is the angleformed by the tilt plate wall 59 and the plane of the tilt plate.

Alternatively, the tilt plate can be moved between two positions, bothof which are slanted relative to the dental tool shaft. However, theedges 59 of opening 61 would be formed in the tilt plate so that theyare coaxial about the dental tool in the unlocked position, and contactthe dental tool when the tilt plate is pivoted to its locked position.

The tilt plate wall 59 of FIGS. 18 and 19 contacts the tool at only onepoint along each edge. It is this point of contact with the tool which"grabs" the tool to hold the tool in the tube 37. FIGS. 19 and 20 showalternate tilt plates 55' and 55". These tilt plates are substantiallyidentical to tilt plate 55. However, their walls 59' and 59" areprovided with cutouts 69. These cutouts have comers 71 which defineadded edges which can grab the tool to better hold the tool in the burtube 37. As shown, tilt plate 55' has two cutouts and tilt plate 55" hasfour cutouts. Fewer or more cutouts could be provided and the cutoutscould be differently shaped. For example, they could be shaped astriangles.

Tilt plate 55 is normally urged to its locking position by a spring 73positioned below the tilt plate. Spring 73 is received in channel 40 andhas one end seated on the floor 38 of gear head 33 and the other end inoperative contact with finger 63 of the tilt plate. The spring thusurges the tilt plate finger upwardly, tilting the plate relative to thetool, biasing the tilt plate to its locked position.

A spacer 75 (FIGS. 8-9), which is slidably journaled about bur tube 35,is positioned between spring 73 and tilt plate finger 63. Spacer 75 hasa lower surface 77 against which spring 73 bears and an upper surface 79which is in contact with the tilt plate finger 63. A slit 81 extendsdownwardly from spacer top surface 79, and is positioned so that it willbe aligned with tilt plate finger 65. Slit 81 has a width slightlylarger than finger 65 and is provided so that the spacer will notcontact finger 65. This ensures that the spacer will not bear againstfinger 65 if it protrudes from bur tube opening 47 so that finger 65 canact as a pivot point for the tilt plate.

A tilt plate pusher 85 (shown more clearly in FIG. 7) is journaled aboutbur tube 37 above tilt plate finger 63. Pusher 85 has a generallycylindrical body 87 and a pair of upwardly extending arms 89. Arms 89are slidably received in bur tube head grooves 51 to rotationally fixpusher 85 with respect to tube 37. The body 87 of pusher 85 isapproximately equal to the distance between the top of opening 45 andthe bottom of bur tube head 41. The body has a lower surface 91 which,when the pusher is urged downwardly, contacts the tilt plate finger 63to move the tilt plate from its locked (tilted) position to its unlocked(horizontal) position.

Ball bearing 95 is press fitted about the top of tube 37 and is coveredin the top of head 7 by a cap 97. Cap 97 has an annular wall 99 whichsurrounds bearing 95. Wall 99 is externally threaded so that the cap canbe screwed into an internally threaded counter-bore 101 of head 7. Thecap is preferably threaded into head 7 until shoulder 99a contacts theupper surface 102a of head 7. Cap 97 has a radially inwardly extendingsurface 103 which is adjacent the top of bearing 95. A push button 105is received in cap 97 for axial movement. Push button 105 has adownwardly extending outer wall 109 and a pedestal 111 centrally locatedwith respect to the wall 109. Pedestal 111 and wall 109 define a channel112 in which a wave spring 113 is received. Spring 113 extends betweencap surface 103 and the top of the push button channel 112 to normallybias the push button upwardly.

The push button pedestal 111 and the tilt plate pusher arms 89 are sizedso that when the push button is pressed, pedestal 111 will be urgeddownwardly to contact arms 89 of tilt plate pusher 85. The distance oftravel of the button is sufficient to urge pusher 85 downwardly adistance far enough to move tilt plate 55 from its locked to itsunlocked position. When the push button 105 is released, spring 113urges push button 105 upwardly and spring 73 urges tilt plate 55 to itslocked position.

The force of the spring 73 is sufficiently strong to prevent the toolfrom being pulled from the bur tube and to prevent undue radial slippageof the tool within the tube while the handpiece is being operated. Chuckretention was tested in a ten minute cutting test. When the handpiecewas operated at 8,000 rpm, there was virtually no axial slippage of thedental tool and no rotational slippage. When it was operated at 50,000rpm, there was virtually no axial slippage and only slight rotationalslippage. As can be appreciated, the force with which the tilt plategabs the tool substantially prevents axial and rotational slippage ofthe tool at operational speeds. Further, because only light pressure isneeded to depress the push button, the chuck is easily operated.

A second embodiment 21' of the chuck assembly is shown in FIG. 11. As inFIG. 1, the angle head 7 is hollow and rotatably receives a driven gear29' which meshes with drive gear 9. Gear 29' has a hollow stem 31' whichis press fitted in ball bearing 25 and a hollow head 33'. As with gear29, head 33' has a diameter greater than stem 31' and defines a channel40' having a floor 38'. The wall of gear head 33' is stepped to define ashoulder 201 above floor 38'. The shoulder 201 separates the inside ofthe hollow gear into an upper section and a lower section. The uppersection has a wider diameter than the lower section to accommodate thespacer 75'.

A bur tube 37' is received in gear stem 31' and extends upwardly throughthe head 7. Bur tube 37' has a bore 42' and a shoulder 54' formed nearthe top of the tube 37' to prevent the tool 23 from extending throughthe tube. A first opening 45' and a second smaller opening 47' areformed in tube 37' to receive tilt plate 55 in the same manner the tiltplate is received in bur tube 37. However, the openings 45' and 47' arepositioned to be in the channel 40' defined by gear head 33' and burtube 37', so that the ann 63 of tilt plate 55 extends into the channel40'.

The tilt pusher 85' is journaled about bur tube 37' to slide axiallywith respect to tube 37'. The tilt plate pusher 85' includes an upperportion 203 which has an inner wall adjacent the bur tube 37' and alower portion 205 which has an inner wall spaced from bur tube 37' todefine a channel 207. The tilt plate pusher forms a shoulder 209 wherethe upper and lower portions join.

Spring 73 is received in channel 207 to extend between the tilt plate 55and the shoulder 209A of bur tube 37'. A spring spacer 75' is insertedbetween the spring and the tilt plate. Spacer 75' is substantiallyidentical to spacer 75, and includes a slot 81' so that spacer 75 willnot positively contact tilt plate arm 65.

The operation of chuck 21' is similar to that of chuck 21. Chuck 21'differs from chuck 21 in that spring 73 is positioned above the tiltplate, rather than below the tilt plate. The spring 73 thus urges thetilt plate downwardly to bias the tilt plate to its normally lockedposition. Further, the tilt plate 55 of chuck 21' is reversed relativeto tilt plate 55 of chuck 21. Arm 63 of tilt plate 55 extends throughsmaller bur tube opening 47' rather than 45' and short arm 65 extendsthrough the larger bur tube opening 45'. Thus, tilt plate pusher 85'contacts the long arm 63 of the tilt plate 55 and arm 63 acts as thepivot point, rather than arm 65.

A third embodiment of the chuck is shown in FIGS. 12-17. The angle 3receives a chuck 21" in its head 7 which operates similarly to chucks 21and 21' to releasably secure tool 23 therein. Chuck 21" includes a burtube 37" press fit in ball bearings 25 and 95 to be rotatable in head 7.Bur tube 37" has openings 300 formed near the top of the tube.Preferably there are two such openings spaced 180° apart. Driven gear29" is fixed about the bur robe 37" to mesh with drive gear 9 to rotatethe chuck 21" and the tool 23. Tube 37" has an internal shoulder 500formed at the bottom thereof.

A tilt plate pusher 85" is received within bur robe 37". It includes ahead 303 having an outer diameter slightly smaller than the innerdiameter of bur tube 37" so that it may slide within the bur tube. Ahole 305 is formed in head 303 near the top thereof. As seen in FIG. 13,the hole 305 is about half the size of, and axially aligned with, theopenings 300 of bur tube 37". Drive pins 306 are passed through openings300 and 305 to rotationally fix tilt plate pusher 85" to bur tube 37".Bur tube openings 300 are axially elongate, and provide a vertical pathof travel for pins 306, so that tilt plate pusher 85" may movevertically relative to tube 37" to move tilt plate 55 between its lockedand unlocked positions. The outer diameter of tube 301 is stepped as at307 to form a lower body section 309. Body section 309, with bur robe37", defines an annular channel 311 below step 307. A pair of holes 45"and 47" are formed near the bottom of tube 301 to receive the tilt plate55. A flange 319 is spaced above head 303 to define a groove 321 withflange 317. Flange 319 has an outer diameter smaller than the outerdiameter of bur tube 37".

Spring 73 and a spring spacer 75" are received about tilt plate pusher85" in channel 311. Tilt plate 55 is inserted through robe openings 45"and 47" so that the spring and spring spacer are positioned above tiltplate 55 between the tilt plate and shoulder 307 of tube 85".

An offset retaining ring 331 is received in groove 321 of tilt platepusher 85" and extends over ball bearing 95. Retaining ring 331 has anannular shoulder 332 defining an opening 333 which is partially receivedin groove 321. The diameter of opening 333 is slightly larger than theouter diameter of flange 319 so that the flange may slide throughopening 333 when the flange is aligned with opening 333. Push button 105is then inserted in head cap 97" above tilt plate pusher 85" so that itmay push the assembly downwardly when depressed. A button spring washer113 is received between bearing 95 and the push button 105 to urge thebutton normally upwardly.

The operation of chuck 21" is shown in FIGS. 12A-C. When the handpieceis in use, retaining ring 331 is spun radially outwardly, causingretaining ring shoulder 332 to slide into tilt plate pusher groove 321to hold the tilt plate pusher vertically in bur tube 37". When theoperator presses down on push button 105 to release the dental tool,beveled edges 501 of the push button contact the upper edges of ring331, to center the ring 331 and ring opening 333 with respect to thetilt plate pusher flange 319, as shown in FIG. 12B. As can be seen, theshoulder 332 and groove 321 are sized so that the shoulder 332 will notbe within the groove when the retaining ring is centered. As the pushbutton is farther depressed, the tilt plate pusher is urged downwardlyto urge tilt plate 55 downwardly until tilt plate arm 63 contacts burrobe shoulder 500. The tilt plate will then pivot about its arm 65 fromits locked, to its unlocked, position, as shown in FIG. 12C.

A fourth embodiment 21'" of the chuck assembly is shown in FIG. 21. Asbefore, chuck 21'" is press fit in lower and upper ball bearings 25 and95 so that it may rotate within head 7 to rotate a tool. The chuck 21'"includes a driven gear 29'" which is substantially identical to gear29'. However, it includes a shoulder 401 formed about halfway along itsstem 31'".

A bur tube 37'" is press fit in gear stem 31'". Bur tube 37'" is similarto bur tube 37', however, it includes a shoulder 403 which seats on gearstem shoulder 401 and internal threads 405 formed above gear 29'". Burtube 37'" has openings 45'" and 47'" to receive tilt plate 55transversely in the bur tube.

A spacer 75'" is journaled internally of bur tube 37'" above tilt plate55. Spacer 75'" has a lower surface 77'" which is in operative contactwith tilt plate finger 63. A slot 81'" is provided in the wall of thespacer so that the spacer will not contact tilt plate finger 65. Thisallows the finger 65 to act as a pivot point for the tilt plate withoutinterference from the spacer. A second slot 82'" is provided in spacer75'" opposite of slot 81'".

A tilt plate pusher 85'" is received within bur tube 37'" above spacer75'". Pusher 85'" is formed as a tube having a cylindrical wall 407 anda top 409. Wall 407 has external threads 411 which mesh with threads 405of bur tube 37'". By rotating pusher 85'" in one direction (for examplecounter clockwise), pusher 85'", bears down on spacer 75'", causing tiltplate 55 to tilt to its locked position, shown in FIG. 21. Becausespacer 75'" is separate from pusher 85'", rotation of pusher 85'" willnot cause spacer 75'" to rotate. Thus, the slot 81'" of spacer 75'" willstay in alignment with the tilt plate finger 65. If desired, spacer 75'"could be rotationally fixed to bur tube 37'", using a pin received in anelongate channel, for example, to ensure that the slot 81'" remains inalignment with the finger 65. By rotating pusher 85'" in the oppositedirection (clockwise), the pusher is brought off the spacer, and thetilt plate is allowed to fall to its horizontal, unlocked position.Although not used, a spring could be provided beneath the tilt plate tobias the tilt plate to its unlocked position when the pusher 85'" isrotated to unlock the flit plate. Unlike the chucks 21, 21', and 21",pusher 85'" places the chuck in its locked position and positivelyretains the tilt plate in the locked position. That is, chuck 21'" doesnot rely on spring forces, as do chucks 21, 21', and 21", to maintainthe tilt plate in its locked position. Thus, a greater force can beexerted by the tilt plate on the tool, creating a tighter "grip" by thetilt plate of the tool.

A push button 105'" is used by the operator to rotate the pusher 85'".Push button 105'" is rotatably received in a cap 97'" which closes head7. Push button 105'" has a rib 111'" which is received in a groove 413formed in the top 409 of pusher 85'". Push button 105'" is biasedupwardly by a wave spring 113'" which biases push button 105'" upwardlyso that rib 111'" is normally out of groove 413. Thus, by pressing downon push button 105'", rib 111'" can be engaged into groove 413, and thenpush button 105 is rotated to rotate the pusher 85'". The sides of thepush button 105'" could be knurled to facilitate turning of the pushbutton, or a portion of the button 105'" could be formed as a bail to bepivoted up and used as a handle in turning the button 105'".

Alternatively, chuck 21'" can be operated using the handpiece motor. Theoperator can press down on the push button to hold the tilt plate pusheragainst rotation, by aligning the push button rib with the tilt platepusher groove. He can then operate the handpiece motor to turn the burtube 37'". This will cause the bur tube to rotate relative to the tiltplate pusher, and the tilt plate pusher will subsequently movevertically relative to the bur tube. Handpiece motors generally can beoperated to run in clockwise and counter-clockwise directions, and canthus be used to both lock and release the dental tool. When the dentaltool is being locked in the handpiece, the push button will begin torotate when the tilt plate reaches its locked position. By allowing forrotation of the push button at that point will prevent stripping of thepush button rib and the tilt plate pusher slot, and will inform theoperator that the tilt plate is in its locked position.

To prevent the push button from being rotated by the motor when theoperator locks or unlocks the chuck, the push button is provided with akey extending radially from the push-button vertically along its side.The key is received in a key path in the cap. The interaction of the keyand the key path will prevent the push button from rotating relative tothe cap. The same goal could be achieved by using a square push button,for example. Other polygonal shaped push buttons could also be used toprevent the push button from rotating relative to the cap.

The foregoing embodiments all include a single tilt plate. The chuckscould also be provided with two or more tilt plates, as shown in FIGS.22-25. The use of two or more tilt plates increases the extent to whichthe tilt plates grab or bite the dental tool shaft to create a bettergrip on the shaft. In FIG. 22, two tilt plates are placed one on top ofthe other. The use of two tilt plates, as shown in FIG. 22 will notalter the operation of the chuck used. It will, however, require thatthe bur tube openings through which the tilt plate arms extend beenlarged to accommodate the extra thickness of two or more tilt plates.

In FIGS. 23 and 24, two spaced apart tilt plates are shown. In FIG. 23,the two tilt plates are substantially parallel and pivot in the samedirection. This will require a tilt plate pusher having a side arm, asshown with inwardly directed fingers which push against the tilt platearm when the push button is depressed to release the chuck. It will alsorequire extra sets of bur tube openings to accommodate the spaced aparttilt plate arms.

In FIG. 24, the tilt plates pivot in opposite directions. To operatethis embodiment, a spreader can be positioned between the arms that haveto be spread apart to unlock the chuck. The tilt plate pusher, ratherthan acting directly on the tilt plates, will act on the spreader topush the spreader radially inwardly when the push button is depressed.This will cause the tilt plates to pivot to their unlocked positions. Aspring can be positioned between the other arms of the tilt plates, tobias the arms apart to bias the tilt plates to a normally lockedposition.

In FIGS. 22-24, the tilt plates are all oriented in the same direction.That is, the tilt plate arms extend along the same vertical plane. InFIG. 25, the tilt plates are shown to be rotated with respect to eachother by some degree greater than 0°. In this embodiment, the tilt platepusher will be provided with a push arms which are spaced apart fromeach other to contact the arms of the respective tilt plates.

Turning to FIGS. 26-28, a dental handpiece 601 is shown whichincorporates a push button chucking mechanism to quickly and easilyreleasably secure the shaft of a dental tool or attachment. Hand piece601 includes a multi-part sheath 603 which defines the outer surface ofthe handpiece. A front sheath or head 605 has an axial bore 607 which isstepped inwardly as at 609, 611, and 613, culminating in a forwardopening 615 at the front of the sheath 605 into which a shaft of adental tool can be inserted. This shaft can be the shaft of bur, such asbur 23, shown in FIG. 1. It can also be the shaft 11 extendingrearwardly from the drive gear 9 of FIG. 1. Externally, front sheath 605defines a body 617 having a tapered front end 619. A circumferentialflange 621 is formed midway along the length of sheath 605 and has asloped outer surface. Rearwardly of flange 621, sheath 605 is externallythreaded, as at 623. Forwardly of flange 621, a bore 625 is formed whichreceives an orientation pin 627. Pin 627 functions to preventattachments, such as prophy angles, from rotating on the handpieceduring use, as is known in the art.

A center sheath or arm 631 threadedly receives front sheath 605. Sheath631 is hollow, defining a bore 632 having an internally threaded frontportion 633 into which threaded portion 623 of sheath 605 is screwed.Sheath 631 is stepped internally, as at 635 to define a bore 637. Aninternal shoulder 638 is defined in bore 637, near the back thereof.Externally, the front portion 639 of center sheath 631 is sloped to forma smooth transition with the outer surface of front sheath 605. Sheath631 is stepped at 641 to define a center section 643, and at 645 todefine a back portion 647 which is externally threaded. Center portion643 has two opposing flat sides 649 which are joined by arced surfaces651. A blind bore 653 is formed in one of the surfaces 651 to receive aspring 655. As can be seen best in FIGS. 26 and 28, rear portion 647 isnot centered with respect to center portion 643. The shoulder 645, whichforms the back surface of center portion 643, has a bottom which extendsfarther from the center of bore 637 than does the top of the shoulder;top and bottom being made with reference to the drawings. The bore 653is formed in the top arced surface 651. Generally rectangular openings657 are formed at the front of center section 643 on flat surfaces 649.Preferably, openings 657 extend rearwardly from shoulder 641.

A push button 661 is slidably received about center section 643 ofsheath 631. Push button 661 defines a generally hollow cylinder whichhas opposing flat inner surfaces 663 joined by arced surfaces 665. Thelength of push button surfaces 661 are larger than sheath center sectionsurfaces 649, so that push button 663 may slide vertically relative tocenter section 643. Push button 661 is biased upwardly by spring 655, asshown in FIG. 26. The outer circumference of push button 661 issubstantially equal to the outer circumference of center sheath forwardsection 639, and spring 655 operates to normally maintain push button inthis position. Push button 661 has an indentation 667 formed in the topthereof, which is positioned to be above spring 655. Indentation 667defines an indicia which informs the operator where to press the pushbutton to operate the chuck, as will be described below.

Push button 661 has a front surface 669 having an arced or chamferedcutout 671 formed in front surface 669 at the junction between surface669 and internal flat surfaces 663. Cutout 671 is positioned to becentered over opening 657 in sheath center section 643 when the pushbutton is in its normal position. The surface of cutout 671 preferablydefines a segment of a sphere. Preferably, there are two such cutouts671, one for each sheath opening 657.

A rear sheath 681 is threadedly secured to the center sheath threadedportion 647 and is screwed onto the center sheath to abut center sheathshoulder 645. Rear sheath 681 has an outer diameter, at the frontthereof, substantially equal to the outer diameter of the back of thecenter sheath's forward portion 639. The rear sheath is spaced from thecenter sheath forward portion, and the two parts cooperated to define anannular slot 683 in which the push button slides. Rear sheath 681 has agenerally cylindrical forward portion and a flared back portion 687.Sheath 685 has a forward bore 689 which is threaded, as at 691, at thefront thereof. At the back of threads 691, a flange 693 extends radiallyinwardly, into bore 689. Rearwardly of bore 689, sheath 681 defines alarger diameter bore 695 having internal threads 697 at its front. Bore695 ends in a forward front shoulder 699 which separates bores 689 and695. Bore 695 is sufficiently wide so that sheath 681 may be slidablyplaced over a dental motor unit, to be secured thereto, as is known inthe art.

Sheath 603 rotatably houses a chuck 701 which releasably receives theshaft of a dental tool or attachment. Chuck 701 includes a bur tube 703having a head 705 and a rearwardly extending shaft 707. Head 705 ishollow, defining a bore 709 sized to receive the dental tool orattachment shaft. As in the bur tubes of FIGS. 1 and 11, bur tube head705 has a first large opening 711 and a second smaller opening 713 whichreceives a tilt plate 715. Tilt plate 715 has an opening 717 throughwhich the dental tool or attachment shaft extends. A first arm 719 oftilt plate 715 is received in larger head opening 711 and extendsthrough smaller head opening 713. A longer arm 721 of plate 715 isreceived in larger head opening 711. Because the openings 711 and 713are of different sizes, tilt plate 715 can be tilted, as will beexplained below, to move between a position in which the walls, definingopening 717, are substantially coaxial about the dental tool shaft toallow the dental tool to be placed on or removed from the handpiece 601,and a second position in which the walls defining the opening 717 areoriented to engage, or bite into, the dental tool or attachment shaft,to secure the shaft in the chuck for use.

A tilt plate pusher 722 is slidably received about bur robe 703. Tiltplate pusher 722 is substantially hollow, defining a bore 723 whichextends from the front of tilt plate pusher 722 to a point near the backof the tilt plate pusher. Bore 723 has a diameter slightly larger thanthe diameter of bur tube head 705, so that the tilt plate pusher mayslide over the bur tube head. The diameter of bore 723 is, however,larger than the bur tube shaft 707, and defines an annular channel 725with the shaft. Tilt plate pusher 722 has an opening 727 through whichtilt plate arm 721 extends. At its back end, tilt plate pusher 722 has ahead 729 having a substantially semi-spherical outer surface. Head 729is larger in diameter than the outer diameter of pusher 722, and definesa shoulder or flange 731. When the handpiece 601 is assembled, flange731 extends through openings 657 in center sheath 631, as will bedescribed below. Tilt plate pusher head 729 has a bore 733 which iscoaxial with tilt plate pusher bore 723. Bur tube shaft 707 slidablyextends through head bore 733 to extend rearwardly of head 729.

A spring 734 is received in the annular channel 725 defined by the innersurface of tilt plate pusher bore 723 and bur tube shaft 707. Spring 734is seated, on one end, against the back surface of bur tube head 705,and at another end, against a shoulder 736 at the back of bore 723. Whenthe handpiece is assembled, spring 734 normally urges tilt plate pusher722 rearwardly.

Bur tube 703 has a portion 735 forward of, and narrower than, bur tubehead 705. To rotatably secure chuck 701 in sheath 603, a forward bearing737 is press fit about the bur tube forward portion 735. A rear beating739 is press fit on bur tube shaft 707 intermediate the ends of theshaft. When the handpiece is assembled, the front bearing 737 is seatingon shoulder 611 in the front sheath 605, and the rear bearing 739 isseated against the shoulder 638 in center sheath 631. As can beappreciated, the chuck 701 is sized to fit within the front and centersheaths 605 and 631.

A drive connector 741 is provided to connect the chuck 701 to the drive.Drive 741 includes a robe 743 having a forwardly opening bore 745 and arearwardly opening bore 747. Bore 745 is sized to slidably receive burrobe shaft 707. To rotatably fix bur tube 703 to connector 741, a pin749 is passed through a hole 751 near the back of shaft 707. Tube 743has a pair of axially extending slots 753 though which pin 749 slidablyextends. Slots 753 preferably open to the front of tube 743 tofacilitate connection of the drive connector 741 to bur robe shaft 707,but may be made to be closed, if desired. A connector shaft 755 isslidably received in connector rear bore 747 and extends rearwardly fromthe connector. Connector tube 743 has a pair of slots 757. A pin 759extends though slots 757 and shaft 755 to rotatably fix shaft 755 toconnector tube 743. Shaft 755 has a rear head 760 which is grasped bythe drive, in a manner known in the art, to rotatably drive theconnector, chuck, and hence the dental tool or attachment. A spring 761is received in connector tube rear bore 747 to bias shaft 755 outwardly.As seen in FIG. 26, pin 759 slides in slot 757. Slot 757 is dosed, andthus, spring 761 cannot push shaft 755 out of bore 747. Connector couldbe made as a single piece. However, various drives may extend into therear sheath 681 to varying depths. Thus, connector 741 is designed tohave a variable length. The use of spring 761 will urge shaft 755normally outwardly, and the drive can urge the shaft inwardly, ifnecessary. A third bearing 761 is press fit about robe 743 and ispositioned on robe 743 so that it will slidably seat against shoulder693 in rear sheath bore 689. A lock nut 763, having external threads 765is threaded onto threads 697 in rear sheath bore 695 until lock nutabuts shoulder 699. Lock nut 763 has a forward surface 767 having anannular width larger than the width of shoulder 699. Lock nut 763, thusholds bearing 761, and hence connector 741, in placed in sheath 603.

To assemble handpiece 601, from bearing 737 is press fit on bur robefront portion 735. Spring 734 is placed about bur tube shaft 707 and thetilt plate pusher 721 is place over bur robe 703. Tilt plate 715 is thenpassed through tilt plate pusher opening 727 and into bur tube 703,through bur tube opening 713. Bearing 739 is press fit on shaft 707 andpin 749 is pressed through bur tube shaft 707. The chuck 701, is theinserted into front sheath 605 so that from beating 737 rests againstshoulder 611. The center sheath 631 is secured to front sheath 605, sothat back bearing 739 is seated against shoulder 638 to secure chuck 701in the sheath. When the chuck is in place in the sheath, tilt platepusher head 729 extends through center sheath openings 657. Spring 655is inserted in center sheath bore 651, and push button 661 is slid overcenter sheath center portion 643. The rear sheath 681 is then secured tocenter sheath 631 to secure push button 661 in place.

Drive connector 741 is slidably placed in rear sheath 681 so thatbearing 761 sits on flange 693. Connector 741 is then secured in sheath681 by lock nut 763. Connector 741 may be placed in sheath 681 eitherbefore or after the rear sheath is secured to the center sheath.

To operate the chuck, the push button 661 is depressed in channel 683.When the push button is depressed, the push button chamfered edges 671will slide against tilt plate pusher head 731 to urge the tilt plateforward. When the tilt plate is urged forward, the rear edge of tiltplate pusher opening 727 will contact tilt plate arm 721 and move thetilt plate to its first, unlocked position, to allow a dental tool orattachment to be inserted in, or removed from, bur tube 703. When thepush button is released, spring 655 will urge the push button upwardlyto its normal position. Because bur tube 703 is axially fixed in sheath603, spring 734, in channel 725, will then urge tilt plate pusherrearwardly. The front edge of tilt plate pusher opening 727 will thencontact tilt plate arm 721 and move the tilt plate to its tilted,locking position, to secure a dental tool or attachment shaft in the burtube.

As can be appreciated, the preferred embodiments provide for a chuckwhich is easy to operate. Importantly, the head is closed, except forthe bottom of the head where the tool is inserted, so that few to nocontaminants can enter the head 7.

As variations within the scope of the appended claims may be apparent tothose skilled in the art, the foregoing description is set forth onlyfor illustrative purposes and is not meant to be limiting. For example,although the chuck of the present invention has been described in a geardriven system, it will be appreciated that it could be used equally wellin a turbine driven system. All that need be done is to replace thedriven gear with turbine blades and provide an air tube through thesleeve of the handpiece to deliver driving air to the turbine blades.Spring spacer 75 facilitates application of the spring force exerted byspring 73. The spring spacer, however, could be deleted from the chuckassembly. In the fourth embodiment, more than one rib can be provided onthe under surface of the push button which will be received by an equalnumber of grooves formed in the tilt plate pusher. The increased numberof ribs and grooves may create a better hold of the push button on thetilt plate pusher. In the handpiece of FIGS. 26-28, the chuck could bedesigned so that the tilt plate pusher slides inside of the bur tube,rather than outside of the bur tube as shown. The push button of thespring-loaded embodiments may equivalently be replaced by a camminglever such as the lever of the above-mentioned Heil U.S. Pat. No.5,040,980. It will also be apparent to those skilled in the art that thechucks of the present invention could be used in conjunction withmedical instruments, such as surgical drills. These examples are merelyillustrative.

We claim:
 1. A dental handpiece for rotatably driving a dental tool or adental attachment, the handpiece including a sheath housing a chuckwhich releasably holds said dental tool or dental attachment to saidhandpiece and a push button in operative contact with said chuck tooperate said chuck; said sheath defining, in an outer surface thereof,an annular slot in which said push button slides, said slot having apair of opposing flat surfaces, said surfaces being offset from a centerof said sheath; said push button generally defining a ring having a pairof inner flat surfaces, said push button flat surfaces being longer thansaid sheath flat surfaces, so that said push button may be movedrelative to said sheath between a first position in which said chuck isin a locking mode, and a second position in which said chuck is in arelease mode; said push button being normally biased to said firstposition.
 2. The dental handpiece of claim 1 wherein said chuck includesa bur tube rotatably received in said sheath; said bur tube having aforward opening sized to receive a shaft of said dental attachment ordental tool; a pair of oppositely disposed openings in a side of saidbur tube; a tilt plate which is pivotably received in said bur tube,said tilt plate having a first arm received in one of said bur tubeopenings and a second arm received in the other of said bur tubeopenings, one of said bur tube openings being larger than the other toallow for tilting of said tilt plate; said tilt plate having a centralopening defined by at least one edge through which said shaft of saiddental tool or attachment extends, said tilt plate being movable betweena locked position in which said edge contacts said shaft to secure saiddental tool or attachment to said handpiece, and an unlocked position inwhich said edge is generally coaxial with said shaft, to allow movementof said shaft relative to said handpiece; and a tilt plate pusheraxially slidable relative to said bur tube, said tilt plate pusher beingin operative contact with said push button and said tilt plate, saidtilt plat pusher being moved by said push button to move said tilt platebetween its locked and unlocked positions.
 3. The handpiece of claim 2wherein said sheath defines at least one slot placing an interior ofsaid sheath in communication with said sheath annular slot; said tiltplate pusher having..a head extending through said slot to be inoperative contact with said push button, such that when said push buttonis pressed, said push button will press against said tilt plate head andmove said tilt plate axially in said sheath.
 4. The handpiece of claim 3wherein said tilt plate pusher head has a generally semi-sphericalsurface; said push button having a surface defining a chamfered cutout,said cutout cooperating with said tilt plate pusher head to urge saidtilt plate pusher axially when said push button is pressed.
 5. Thehandpiece of claim 4 wherein said tilt plate pusher has an opening in aside thereof through which an arm of said tilt plate extends, said slotbeing positioned such that when said tilt pat pusher is moved axiallyforwardly, a rear edge of said slot contacts said tilt plate arm to movesaid tilt plate from its locked to its unlocked position.
 6. Thehandpiece of claim 5 wherein said tilt plate pusher slot has a secondedge defining an end of said slot opposite said slot rear edge, saidtilt plate pusher being biased axially rearwardly; said tilt platepusher slot being sized such that said second edge will contact saidtilt plate arm to move said tilt plate from its unlocked to its lockedposition.
 7. The handpiece of claim 6 wherein said tilt plate pusherhead has a bore therethrough; said bur tube including a rearwardlyextending shaft which is operatively connected to a motor unit, saidmotor unit imparting rotational motion to said chuck to drive saiddental tool or attachment.
 8. The handpiece of claim 7 including a driveconnector which connects said bur tube shaft to said drive; said driveconnector having a rearwardly extending shaft which is received by saiddrive.
 9. The handpiece of claim 8 wherein said drive connector shaft isaxially slidable to accommodate differently sized drives.